Percentage Calculator
Example: 25 is 20% of 125 • 15% of 80 = 12
Calculate what percent X is of Y, find X% of a number, determine percentage change, and solve other common percentage problems.
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How We Calculate This
This calculator uses standard percentage formulas: Percentage = (Part ÷ Whole) × 100, Part = (Percentage × Whole) ÷ 100, Percentage Change = ((New - Old) ÷ Old) × 100.
Methodology last reviewed: September 2025. How SparkCalc works
Sources: Encyclopaedia Britannica: Percentage · Encyclopaedia Britannica: Ratio and Proportion · NIST: Special Publication 811: Guide for the Use of the International System of Units (SI)
Frequently Asked Questions
How do I calculate percentage?
To find what percent X is of Y: (X ÷ Y) × 100. To find X% of Y: (X ÷ 100) × Y. For percentage change: ((New - Old) ÷ Old) × 100.
How do I calculate percentage increase?
Percentage Increase = ((New Value - Original Value) ÷ Original Value) × 100. A price going from $80 to $100 is a 25% increase.
How do I calculate percentage decrease?
Percentage Decrease = ((Original Value - New Value) ÷ Original Value) × 100. A price going from $100 to $80 is a 20% decrease.
What is the difference between percentage and percentile?
A percentage is a fraction of 100 (e.g., 25% = 25/100). A percentile indicates a value below which a percentage of data falls (e.g., 90th percentile means 90% of values are below this point).
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